diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index 3b1cd740057..a5c5f12f10b 100644
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@@ -1,4 +1,4 @@
-
+
@@ -78,6 +78,7 @@
+
diff --git a/doc/src/sgml/gin.sgml b/doc/src/sgml/gin.sgml
new file mode 100644
index 00000000000..4420fcd0ab9
--- /dev/null
+++ b/doc/src/sgml/gin.sgml
@@ -0,0 +1,135 @@
+
+
+
+GIN Indexes
+
+
+ index
+ GIN
+
+
+
+ Introduction
+
+
+ GIN stands for Generalized Inverted Index. It is
+ an index structure storing a set of (key, posting list) pairs, where
+ 'posting list' is a set of documents in which the key occurs.
+
+
+
+ It is generalized in the sense that a GIN index
+ does not need to be aware of the operation that it accelerates.
+ Instead, it uses custom strategies defined for particular data types.
+
+
+
+ One advantage of GIN is that it allows the development
+ of custom data types with the appropriate access methods, by
+ an expert in the domain of the data type, rather than a database expert.
+ This is much the same advantage as using GiST.
+
+
+
+ The GIN
+ implementation in PostgreSQL is primarily
+ maintained by Teodor Sigaev and Oleg Bartunov, and there is more
+ information on their
+ website.
+
+
+
+
+
+ Extensibility
+
+
+ The GIN interface has a high level of abstraction,
+ requiring the access method implementer to only implement the semantics of
+ the data type being accessed. The GIN layer itself
+ takes care of concurrency, logging and searching the tree structure.
+
+
+
+ All it takes to get a GIN access method working
+ is to implement four user-defined methods, which define the behavior of
+ keys in the tree. In short, GIN combines extensibility
+ along with generality, code reuse, and a clean interface.
+
+
+
+
+
+ Implementation
+
+
+ There are four methods that an index operator class for
+ GIN must provide:
+
+
+
+
+ compare
+
+
+
+
+
+
+
+ extract value
+
+
+
+
+
+
+
+ extract query
+
+
+
+
+
+
+
+ consistent
+
+
+
+
+
+
+
+
+
+
+
+ Examples
+
+
+ The PostgreSQL source distribution includes
+ GIN classes for one-dimensional arrays of all internal
+ types. The following
+ contrib modules also contain GIN
+ operator classes:
+
+
+
+
+ intarray
+
+ Enhanced support for int4[]
+
+
+
+
+ tsearch2
+
+ Support for inverted text indexing. This is much faster for very
+ large, mostly-static sets of documents.
+
+
+
+
+
diff --git a/doc/src/sgml/xindex.sgml b/doc/src/sgml/xindex.sgml
index 9c52202ea04..35e5137eaec 100644
--- a/doc/src/sgml/xindex.sgml
+++ b/doc/src/sgml/xindex.sgml
@@ -1,4 +1,4 @@
-
+
Interfacing Extensions To Indexes
@@ -380,6 +380,41 @@
+
+ GIN indexes require four support functions,
+ shown in .
+
+
+
+ GIN Support Functions
+
+
+
+ Function
+ Support Number
+
+
+
+
+ compare
+ 1
+
+
+ extract value
+ 2
+
+
+ extract query
+ 3
+
+
+ consistent
+ 4
+
+
+
+
+
Unlike strategy operators, support functions return whichever data
type the particular index method expects; for example in the case